What converter do I need to use US guitar amp in UK?

June 22, 2020 5:28 AM

I live in the UK, and recently procured a US-made small guitar amp, wired for US use. I am horribly ignorant about electrical currents. I presume I need some sort of converter (beyond the basic US/UK plug converter) so I can rock out without blowing up my apartment. But which one do I need? Amp is a Harmony Model H510. Specs are 117V 60Hz 22 Amp. Any tips really appreciated!
posted by Jellybean_Slybun to Grab Bag (9 answers total)

You need a step down transformer like this. That one is rated for 4A output. Are you sure about the 22 amp number? That sounds really high. Is it maybe 2.2 amps? If so, you could probably use the slightly cheaper 300 VA version, but if it were me I’d use the larger one. Another option would be to have a shop rewire or replace the transformer that’s inside the amp. The rewire/replace would depend on the wiring of the existing transformer.
posted by doctord at 6:10 AM on June 22, 2020 [1 favorite]

Response by poster: Thank you!

It does look like it says 22 Amps, and a review such as this one confirms it.
posted by Jellybean_Slybun at 6:15 AM on June 22, 2020

If it were me, I'd have it converted to 220V by someone who knows vintage electronics. One of the dangers is that vintage amps are often not earthed properly (to current standards). Just adding a step-down transformer in front doesn't fix that, and there may be other issues such as elderly capacitors that might need replacing.

There are affordable 110V transformers (close enough to 117V) with a decent power output available for powering builders' tools - you'd need at least 2.5kW given your amp's spec. I'm not sure how well one of those will work in terms of electrical noise, although builders often plug 110V radios into them, so there's always the option of picking one of those up from Screwfix or Toolstation - both have a decent returns policy.
posted by pipeski at 6:25 AM on June 22, 2020

If it was 117V and 22A then the spec would read 2574A, not 25.74. I can't see a small guitar amp drawing 2.5 kilowatts, that's a PA system.

I agree with doctord it's probably 2.2A. And I agree to get the 500VA version they link to.

Remember that if you get the amp transformer rewired or replaced instead, that might affect the resale value of the amp, so an external solution like doctord suggests is perhaps better. Pipeski makes some excellent points about earthing, however.
posted by dowcrag at 6:26 AM on June 22, 2020 [2 favorites]

Or if it was 0.22 amps then 0.22 x 117 would give the 25.74W number in the link you posted. But at this point I’d 2nd pipeski about having someone local look at it rather than us speculating based on 2nd hand information.
posted by doctord at 6:34 AM on June 22, 2020 [1 favorite]

Here's a picture from a different Harmony amp. The 'house style' would be .22 AMPS.
posted by StephenB at 6:46 AM on June 22, 2020 [1 favorite]

Uh, yeah, that's a little 5 watt guitar amp - no way is it pulling 22 amps.

I've run entire bands with Ampeg SVT rigs and Marshall half-stacks on a single 20-amp circuit.

I think StephenB is right, it's more likely .22 amps with the "." rubbed off.

Is there a fuse? Check that rating.
posted by soundguy99 at 7:27 AM on June 22, 2020 [1 favorite]

Best answer: It reads .22A (so 0.22A, not 22A), so a power draw of 25 Watts, which is totally plausible for an amp this size. 22A (2.5kW) would be the power draw for a PA stack, and nudging the volume knob off zero would have your eardrums meeting in the middle of your skull with the first chord. It would also have that speaker cone whacking against the frame and the voice coil burning up.

A 100VA step-down transformer is utterly sufficient; more doesn't hurt (except your wallet and your muscles).
posted by Stoneshop at 7:29 AM on June 22, 2020 [3 favorites]

Response by poster: I suspect the . got erased from the start of .22 on my amp! It’s pretty tarnished.

Thanks for the help everyone
posted by Jellybean_Slybun at 7:51 AM on June 22, 2020